SETI in the Infrared

byPaul GilsteronNovember 6, 2018

One of the problems with optical SETI is interstellar extinction, the absorption and scattering of electromagnetic radiation. Extinction can play havoc with astronomical observations coping with gas and dust between the stars. The NIROSETI project (Near-Infrared Optical SETI) run by Shelley Wright (UC-San Diego) and team is a way around this problem. The NIROSETI instrument works at near-infrared wavelengths (1000 – 3500 nm), where extinction is far less of a problem. Consider infrared a ‘window’ through dust that would otherwise obscure the view, an advantage of particular interest for studies in the galactic plane.

Would an extraterrestrial civilization hoping to communicate with us choose infrared as the wavelength of choice? We can’t know, but considering its advantages, NIROSETI’s instrument, mounted on the Nickel 1-m telescope at Lick Observatory, is helping us gain coverage in this otherwise neglected (for SETI purposes) band. I had the chance to talk to Dr. Wright at one of the Breakthrough Discuss meetings in Palo Alto, where she made a fine presentation on the subject. Since then my curiosity about infrared SETI has remained high.

Meanwhile, at MIT…

Then this morning I came across graduate student James Clark, who has just published a paper on interstellar beacons in the infrared in the Astrophysical Journal. Working at MIT’s Department of Aeronautics and Astronautics, Clark is not affiliated with NIROSETI. He’s wondering what it would take to punch a signal through to another star, and concludes that a large infrared laser and a telescope through which to focus it would be the tools of choice.

The goal: An infrared signal at least 10 times greater than the Sun’s natural infrared emissions, one that would stand out in any routine astronomical observation of our star and demand further study. Clark believes that a 2-megawatt laser working in conjunction with a 30-meter telescope would produce a signal easily detectable at Proxima Centauri b, while a 1-megawatt laser working through a 45-meter telescope would produce a clear signal at TRAPPIST-1.

But nearby stars are just the beginning, for in Clark’s view, either of these setups would produce a signal that could be detected up to 20,000 light years away, almost to galactic center. All of this may remind you of Philip Lubin’s work, recently described here, on laser propulsion. Depending on the system in play, one of Lubin’s DE-STAR 4 beams would be observed as the brightest star in the sky from 1000 light years away (see Trillion Planet Survey Targets M-31 for more on this). The NIROSETI website makes the same observation about laser visibility:

The most powerful laser beams ever created (e.g. LFEX) can produce optical pulses with 2 petawatts (2.1015W) peak power for an incredibly short duration, approximately one picosecond. Such lasers would outshine our sun by several order of magnitudes if seen by a distant receiver. It can be shown that strong pulsed signals at nanosecond (or faster) intervals can be distinguishable from any known astrophysical sources.

Image: An MIT study proposes that laser technology on Earth could emit a beacon strong enough to attract attention from as far as 20,000 light years away. Credit: MIT.

The kind of system Clarke is talking about is not beyond our capabilities even now:

“This would be a challenging project but not an impossible one,” Clark says. “The kinds of lasers and telescopes that are being built today can produce a detectable signal, so that an astronomer could take one look at our star and immediately see something unusual about its spectrum. I don’t know if intelligent creatures around the sun would be their first guess, but it would certainly attract further attention.”

In terms of current capabilities, we can think about Clark’s 30-meter telescope in relation to plans for telescopes as huge as the 39-meter European Extremely Large Telescope, now under construction in Chile, or the likewise emerging 24-meter Giant Magellan Telescope. How and where to build such a laser is the same sort of issue now being analyzed by Breakthrough Starshot, which conceptualizes a series of small lightsail missions to nearby stars using laser beaming. Caveats include safety issues for both humans and spacecraft equipment. Clark suggests the far side of the Moon would be the ideal place for such an installation.

With METI (Messaging to Extraterrestrial Intelligence) continuing to be controversial, to say the least, whether or not we would ever choose to build an infrared laser as an interstellar beacon is up for question. But Clark’s analysis takes in the question of whether today’s technologies could detect such a signal if a civilization elsewhere put it into play and tried to communicate with us. As we’ve seen in other discussions of interstellar beacons, detection is highly problematic.

“With current survey methods and instruments, it is unlikely that we would actually be lucky enough to image a beacon flash, assuming that extraterrestrials exist and are making them,” Clark says. “However, as the infrared spectra of exoplanets are studied for traces of gases that indicate the viability of life, and as full-sky surveys attain greater coverage and become more rapid, we can be more certain that, if E.T. is phoning, we will detect it.”

We don’t know whether E.T. does astronomical surveys, but we know we do, and we are rapidly moving toward the study of small, rocky exoplanets through the spectra of their atmospheres. Thus Clark’s paper could be seen as a reminder to astronomers that an unusual signal could lurk within their infrared data, one that we should at least be aware of and prepared to analyze. A conversation between nearby stars at a data rate of a few hundred bits per second could eventually result.

With efforts to overcome the obstacle of space, one may try to reduce the obstacles of time such as the dependence on random fortune for the detection of time-constrained signals. If signals are to be used, their chances may be improved by being continuous or repetitive.

They have a laser that is capable of firing 2000 joules in a trillionth of a second. A trillionth of a second! While I don’t know for how long this laser can’t sustain its firing, a civilization on the lookout would just have to be lucky to catch this momentary burst of energy to think: something is funny here, let’s investigate-this seems to be at best somewhat remote as a Beacon.

What are the odds that Oumuamua came through our Sol system when we were just ready enough to detect it, if not actually fly out to it (though we could – and should)?

What are the odds that in a tiny slice of sky Kepler happened to find Tabby’s Star, an object we had never seen before, or at least recognized as unusual by our astronomical standards?

So while the changes of an ETI being able to detect our laser “blips” may be small, they need not be impossible. Especially if we are aiming them at the more populated parts of our galaxy. Plus this along with the fact that a species needs a certain level of advancement to even be able to detect them can act as a filter.

“The most powerful laser beams ever created…can produce optical pulses with 2 petawatts…peak power for an incredibly short duration, approximately one picosecond.” These are EXACTLY the pulse durations Borra and Trottier claimed to have detected in 234 stars. Breakthrough Initiatives promised a re-examination of these stars a couple of years ago with DIFFERENT equipment than that used by Borra and Trottier to eliminate any POSSIBLE calibration issues in the equipment Borra and Trottier used. So far, the results of this follow-up have NOT been published. Are they ON to something? OSETI looks only for one billionth of a second(nanosecond)pulses. Have they been missing out all these years? This is pure speculation, but perhaps a nanosecond is the THRESHOLD upon which messages/data can be transmitted.

Is Breakthrough Listen on to something? Or are they withholding and/or suppressing this information because it does not fit into their idea/plans for SETI?

This has happened before with SETI going back to its earliest days, especially when a few self-appointed authorities on the subject pushed their concepts to the forefront at the expense of other ideas.

Just take a look at the history of Optical SETI, which came out almost at the same time as Radio SETI, only to be sequestered away until the 1990s because the radio astronomers in charge literally thought because humans did not have the proper laser technology at the time that it would not do any good to search for ETI with laser/infrared communications! Even though lasers can be more easily detected than radio and carry a lot more data.

SETI has been give the short end of the stick since its beginnings for a number of reasons. And while collective human minds are a bit more open than they used to be, I am concerned that Breakthrough Listen is just the latest version of yet another self-appointed SETI committee that will dictate how SETI (and METI) should operate, just as Radio SETI dominated the scene for decades.

Yes it is nice they gave money to cash-starved SETI efforts, but since they also hold the purse strings, they can just as easily cut them off or direct the efforts and findings in any direction they want. I would like to see more professional astronomers and scientists having their say in the matter, before we end up with another 30 years of one-way SETI and a peer-banned METI.

Here’s my take on this: Using the APF(i.e. NOT SDSS)they DUPLICATED the Borra/Trottier results, but are now working on the proper INTERPRETATION! The only three things which could CAUSE the anomalities in the Borra/Trottier data are; ONE: Calibration issues with SDSS, which is what ALL of the scientific community ASSUMED to be cause. TWO: A NATURAL process happening within the 234 stars which produces a result ANALOGOUS to picosecond laser pulses. Picosecind laser pulses(and you know what THAT means). As with ANY SETI claim, all other avenues of of persuit must take place before the claim is made public, so they are making a furious attempt ELIMINATE TWO before they can ACCEPT THREE!!!!!! Keep in mind, there is absolutely no reason for them to withhold a PROVEN claim, since this is the PURPOSE of the organization!

Perhaps it is not a deliberate withholding so much as Breakthrough Listen is expecting certain methods in a particular way by ETI. This has been the pattern for most of our modern SETI era, despite the occasional lip service to non-radio means of signaling. Just look at how long it took mainstream SETI to accept optical transmissions and then they tried to rewrite their history to make it look like they had accepted it all along!

While Clark talks about detection up to 20k ly away, there seems no possible way this makes any sense when he later talks about communication. A civ near the galactic center has no way to know what the target star systems should be, other than “habitable”. Sending a signal to us might result in our civilization appearing and disappearing while the beam is in transit, and even that may be unlikely given the distribution of civs in space and time.

If the beam is to be set so the width encompasses the planets in the HZ of a star, then clearly the further the beam is targeted, the larger the number of possible targets, and therefore the lower the frequency of repeats. [ for a 1 ms pulse, sent to 1 bn stars, repeats happen every 11 days. If the pulse was 1 s, the repeat would be every 31 years.] For a small target radius, the repeat rate can be higher, ideally looking unnatural such as a short prime number series of gap length between pulses.
However, for small volumes of space and few target stars, why the need for IR at all? Why not use lasers in the visible spectrum that could be detected more easily?

So while extending the frequency range of SETI searches might be useful, I get the impression that this paper isn’t well thought through logically. I would like to read a better justification for IR, and why NIR rather FIR, compared to radio or optical signaling.

A civilization emerging in proximity to the galactic center will likely be in a milieu of radiation and gravitation quite unlike the comparitive placidity of our neighborhood in a galactic spiral arm. Could they perhaps think that their biology, an adaptation for the threshold of the galactic inferno, may be the standard to judge habitability of beam targets elsewhere?

Yes, yes, but the outstanding Plato had no idea of the effects of prolonged exposure to high frequency radiation… Let alone all the rest… Since you are more of a man than all of the rest of us, please place YOUR child in front of a gamma ray source.

I am guessing you view spiders as automatically bad things, just because and especially because they do not look like humans and tend to creep out most of those primates. What shall we do if most ETI look and act like spiders, plus now they have starships.

The more I see, the more I see that many if not most humans are not ready for what is really out there. That includes even if there are no other living beings.

It seams to be Cargo cult among SETI/METI supporters.
This cult dictate next postulate – there is , somewhere , nice and very advanced up to gods-level ETI , that impatiently waiting (and sending) signal from (to) us, when those superETI will detect our signal , they definitely and immediately will come to the Earth and will teach us, heal us , “save us from us”, etc… us.
The problem is – we are making some doubtful deeds today, but only our decendants will be responsible for our deeds and they could change nothing…

We must be careful about such statements. The Canals of Mars were thought to be artificial because they went in such straight lines. Far more recently, an iceberg was found in Antarctica that looked like a deliberately formed rectangle.

No one is banning METI, particularly because it is not operated by any kind of formal organization – at least at present. There are no actual laws, international or otherwise, against it. Sure there are scientific communities who protest it and others who also voice their negative opinions, but they are not authorities with any kind of actual legal power behind them.

Breakthrough Listen may not be doing any METI themselves, but that is their issue. They also have no authority over anyone else on this planet who does want to conduct METI.

I think that the whole world population should express their consent prior to such an enterprise. They should be made aware that the weapon array currently at our disposal is inadequate to actually pose a threat to “malevolent” intruders. Moreover, since the future inhabitants of our planet can’t convey us their opinion, the whole concept of affirming our presence out there is basically flawed.

You know that suggestion is entirely unrealistic and will therefore negate all METI attempts. Thankfully the very nature of humanity that keeps it so tribal will also ensure that some efforts to communicate with the galaxy have and will happen regardless.

It is impossible, it is false, it is standard “fairy tails” for PR.
False PR It is only way tо justify SETI efforts. In reality communication “with the galaxy” is impossible (with our current technology), It is true that SETI activists prefer to hide from public. It like the next (SETI’s) fairy tails – “negative SETI result it is also good scientific result”, activists do not clarify to public, that negative result – is impossible case for modern SETI approach.

What is most probable METI result – it is disclose our location to someone that we cannot even know their intentions, we can make this mistake “today”, but “tomorrow” our descendants will have problems from cosequences of our deeds.

I find it amusing that while you think all SETI and METI efforts are fruitless endeavors, and imply that there are no aliens in the Cosmos, you worry about a collection of hypothetical ETI who may or may not detect these signals just the same and become a threat to us somewhere in an undetermined future time.

I am sure you already know that Earth life, both intelligent and otherwise, is already detectable from great distances by advanced ETI without humanity having to do anything deliberate here. And humans in the form of our military and radio astronomers have also been letting the galaxy know that we exist via their powerful missile and NEO radar “pings”.

Sure, they are random, but we have been doing it for decades and their signals stand out against the galactic background noise. Even though they contain no data, they do let anyone smart enough know that someone with at least some technology resides on Earth, or did once depending upon when they receive the signals.

We also have to wonder how motivated an ETI would be send starships all the way to Earth and what exactly would motivate them to do this, in particular for any perceived hostile intent. A lot of effort and resources to encounter someone so far across the stars.

If they want mineral resources there are probably a lot of planetoid and comets belts much closer to home. Food and/or slaves? Again, a lot of work for something that has little payoff. Galactic competition? Maybe, but there are 400 billion star systems to choose from. They cannot all be inhabited.

If I am going to worry about something, it makes more sense to worry about the very real and living humans occupying Earth now who have very malevolent intents against all organisms here, either deliberately or through neglect. But then again, hypothetical aliens have always made convenient scapegoats.

Your mistake No.1.
I think SETI effort are really fuitless, when METI are dangerous to humanity, because can bring unexpected problem in the future to our descendants.

…imply that there are no aliens in the Cosmos…

Your mistake No.2.
I suppose there should be ETI in our universe, as sequence my opinion relatively METI efforts. In same time I ready to accept the fact that we are alone, in this case METI still remain serious problem, because dreaming about “contact” METI activist going to use instruments that are in reality – dangerous weapon, I am sure also that METI ideology can be used for noncontrolled laser weapon development, it seams that we live in the period of hybrid wars …

you … know that Earth life… is already detectable from great distances by advanced ETI

Your mistake No.3
At first you are writing about issue like you already found ETI and know very well what they are doing right now :-)
Second, personally my, do not know nothing about this fact (i.e. ETI detected us ;-) And accounting results of our SETI efforts, I can suppose that mysterious ETI has exactly same result :-)
There is hope that ETI scientists are more clever than we are – and prefer not to spend their resources for fruitless SETI…
Third – you are somehow exaggerating the Earth visibility in same time when talking about METI , required power somehow grows to the value that make METI instruments undistinguished from weapon. So why do you so need METI?

…We also have to wonder how motivated an ETI…

Yes, we can wander a lot – in Sci-Fi novels, I enjoy reading this literature. Meanwhile we did not found any ETI, only the Earth habitants – and it will be the bad news for us if ETI are behaving like we are.

…If I am going to worry … about … real and living humans occupying Earth …

In same time you are ready to provide weapon class instruments to the people who can tell fair tails about METI…

At last I now know what it is like to encounter a highly advanced mind with such relentless logic! It is both awesome and humbling.

As a result, no more shall I hold out hope for SETI having even a ghost of chance of detecting other intelligences in the Cosmos. And as for METI, if only I could pull back all those radio transmissions sent into the void but especially the Pioneer and Voyager probes, where I could toss their pitiful efforts into the dustbin of ignominy and history, where they belong! What fools we were to think that such tiny, shiny artifacts might even be found and convey any sort of information about humanity to the superior minds of the galaxy!

I shall also dash against the rocks my clearly now fantasies of renting a radio telescope to broadcast all the music of J. S. Bach all the time into the Milky Way, just to show any ETI with organs that can detect and interpret sound that we mere primates do have some cultural value of a sort. I can also forget that plan to equip a deep space probe with multiple copies of those Golden Plaques and Records, where (upon being launched into the void courtesy of a ride on one of Elon Musk’s rockets) it would use a spring-loaded catapult to randomly shoot those metal messages of “science” into the blackness, even though it is clear now that such actions rival John Paul Sartre in his notions of existential absurdity.

I will then return to my humble abode and burn all my SETI and METI materials, realizing at last that the only true wisdom lies among my fellow humans occupying the third rock from Sol, and that any aliens out there either do not exist or are so far away in time and space that they may as well not matter so far as humanity is concerned. Let us focus instead on all the wonders of human society, for truly they are the final word on reality. All else is some form of illusion.

“Nothing was your own except the few cubic centimetres inside your skull.” ― George Orwell, 1984

In connection to G.Orwell’s quote, I have to admit that mind washing methdology is frequently used by some pop-science activists to advertise SETI (underscore METI) efforts. Properly composed advertising compain brings money. People who know how to earn money – are not fools.

I think it’s a terrific idea to look for signs of extraterrestrial intelligence in the form of short duration laser pulses in the data sets we already have. As for choosing a wavelength, power output and pulse duration at which to transmit our own signals that is a much more difficult question. Especially when we have a whole galaxy as our potential target set. Surely we won’t be spending colossal amounts of money on such an endeavor with no information as to where to aim? I’m a pragmatist as far as this goes. Look for signs of life nearby (and further out if possible) and then sort through the possibilities of intelligence.

With our present knowledges and technology , interstellar Communication is impossible for the distances longer than thens light years. And I do not talk about possibility to decode distant message with massage exchange rate that has so long duration (thens years for one direction message delivery).
As sequence idea to send message to nowhere and adressed to none does not have any excuse.
May be Fermy paradox – is not paradox at all, none of highly developped civilisation send messages simply because it is very bad and not clever idea, only those civilization who understood this fact have a chance to get “long civilization life span” , those civilzations-loosers that decide to wast energy to send message to every directions without realizing who will be an end receiver of this message – vanishing very quickly, so their period of METI activity is very short… i.e. undetectable.

What are you so worried about? No one in SETI or METI is taking your money, as the vast majority of efforts are now privately funded and their history has been a long one of very limited budgets as it is.

If a bunch of individuals want to test the waters, even if their instruments are primitive, who are you or anyone else to say that they cannot? It is their money and time, not yours. If they want to do what you clearly think is shouting into the abyss, that is their business.

The day individual thoughts and actions which clearly harm no one become illegal and controlled by outside authorities is the day we are going to have to worry about a lot more than hypothetical alien intentions. Humans worry about beings that may or may not exist, when it is their own species potential for vice and destruction they should be wary of first and foremost.

What are you so worried about? No one in SETI or METI is taking your money

At first SETI and METI case is significantly different.
If we are talking about SETI – I can accept with almost every your word (in this comment), with only one exclusion – SETI gets some funds from tax payers, but IMO – it should exists only on absolutely private money.

METI is very different case, it can plague lives of our descendants or even stop our civilization. In addition if we will get deep in the information from discussed article, the laser that is supposed to be used for cosmic message delivery – in reality is very dangerous weapon, so there is no need to find evil ETI to use it against humanity – homo sapience can do that “perfectly” (by the way same notes in connection to Breakthrough Starshot).
IMO – any METI implementation in reality have to be absolutely banned on official international level.
Additional problem that METI – is turn to be the real target of SETI activists… We can find proves here in the discussed article , article begins as “SETI in the Infrared” and finished as METI using High power IR laser…

So the article title says SETI when it is really about METI. Why turn this into some kind of conspiracy just to suit your agenda against these subjects when there is none?

I love how you not only stereotype SETI and METI supporters but now you think they are working as some kind of unified force on some hidden agenda. SETI and especially METI has never been unified and most of its practitioners are largely motivated only by expanding human knowledge. If anything I fault them for not often being imaginative enough or expanding beyond the radio spectrum.

There is not any conspiracy – in discussed article everything (SETI-METI connection) is clear and open :-)

…METI … most of its practitioners are largely motivated only by expanding human knowledge…

I suppose there is lot of places on our own planet where huge effort should be done to “expand human knowledge”. Do not think that advanced ETI (who able to get and decode our message) need and can use our knowledge…
“The road to hell is paved with good intentions”.

While astrobiology has become an increasingly mainstream science, it is still grappling with some of the central questions about the existence of life beyond Earth. Jeff Foust reviews a new book that takes a serious look at the field, without taking itself too seriously.

Present day only the Earth biology – is real science, do to fact we have not found any signs of ET life – no any astrobiology is possible , because “astrobiology” still do not have object for studying, i.e. remains Sci-Fi art, not science.

Thank goodness you told me. Yes, we should not speculate on anything that isn’t sitting right in front of our faces, nor should we conduct experiments – thought or otherwise – if it is not permanently, solidly real.

So until we find actual alien life, no scientist should even attempt to model life based on other (real) worlds? They should keep their thoughts to themselves, because that is how we progress, by peer pressured silence, right?

Please tell that to the legit scientists who have and are doing such work just the same whose true colleagues do not seem to be bothered by their taking time and (relatively meager) funds to do so.

Thank you for killing all the cosmic dragons and ghosts. Humanity is so much better for it, as one can tell by watching the news at any given time.

Scientist can model evrything they want.
Fact – modern biology cannot model even our Earth’s life, so I do not believe they can model something different.
In any case this model will have no any connection to prefix ASTRO.
The present situation is next – everything published under nice titles “astrobiology” is hoax.
I do not think that non use of problematic prefix “astro” automatically means stop of science modeling, exploration etc., it only mean return to the policy of true.

“In our next round of transmissions, we’re getting three types of messages ready. One will describe basic chemical principles, we’ll send the periodic table of elements. The second will describe the human body. The third message will go on to describe something about how we engage with one another, altruism. As we design a message for extraterrestrials, we need to ask what we and the extraterrestrials have in common. Well, we have in common the universe itself. So when we look around the universe and try to describe it, we start with what it’s made up of. Hydrogen and helium and carbon and oxygen and phosphorus and all these 200+ chemical elements. Well that’s something that scientists on another world will know about too.”

Radio SETI experiments aim to test the hypothesis that extraterrestrial civilizations emit detectable signals from communication, propulsion, or other technologies. The unprecedented capabilities of next generation radio telescopes, including ngVLA, will allow us to probe hitherto unexplored regions of parameter space, thereby placing meaningful limits on the prevalence of technological civilizations in the Universe (or, if we are fortunate, making one of the most significant discoveries in the history of science).

ngVLA provides critical capabilities in the 10 – 100 GHz range, and will be a valuable complement to SKA in the southern hemisphere, as well as surveying the sky at frequencies underexplored by previous SETI experiments.

In 1974, the Arecibo Observatory made history by beaming the most powerful radio message into deep space ever made. The famous Arecibo Message was designed by the AO 74’s staff, led by Frank Drake, and with the help of the astronomer and famed science communicator Carl Sagan. It contained information about the human race and was intended to be our intergalactic calling card.

“Our society and our technology have changed a lot since 1974,” says Francisco Cordova, the director of the NSF-funded Arecibo Observatory. “So, if we were assembling our message today, what would it say? What would it look like? What one would need to learn to be able to design the right updated message from the earthlings? Those are the questions we are posing to young people around the world through the New Arecibo Message – the global challenge.”

The NSF-funded facility, which is home to the largest fully operational radar telescope on the planet, will launch its online competition later today on the 44th anniversary of the original Arecibo message. Check out the observatory’s website fafter 1 p.m. for details and today’s Google doodle for more information about the first message.

Organizers are seeking innovative ideas from global collaborative efforts of inter-generation, diverse and international teams of students to inspire a new generation of space enthusiasts and define the New Arecibo Message.

But this will be no simple task. In order to get started, teams of up to 10 students in grades kindergarten through college, must decode various clues that will be released online. Like a Chinese puzzle box, teams must learn about Space Sciences, break coded messages and solve brain-puzzles to qualify, get instructions, register and then submit their entries. Arecibo will post its first puzzle on its website and social media channels this afternoon (Nov. 16).

This challenge gives teams nine months to complete their designs. A winner will be announced during the Arecibo Observatory Week activities planned for 2019, which includes the special celebration of the 45th anniversary of the original Arecibo Message.

“We have quite a few surprises in store for participants and we will be sharing more details as the competition progresses,” Cordova says. “We can’t wait to see what our young people across the globe come up with.”

Is There Anybody Out There… Keeping Track of the Weird Stuff We Send Into Space?

A new catalogue attempts to figure out what we’re telling the rest of the universe about ourselves.

by Sarah Laskow

November 19, 2018

There are two main ways to send information out into space—as a transmission or by blasting up a physical object. Through both methods, humans have sent off all sorts of intriguing data about life on Earth.

In 1995, for instance, the National Science Development Agency of Japan transmitted, among other images, one of an alien and an earthling holding hands, in the direction of the Libra constellation. We’ve sent a copy of War of the Worlds to Mars, and models of Lego figures (of the Greek gods Juno and Jupiter, as well as Galileo Galilei) to orbit the planet Jupiter.

The sculptor Forrest Myers reported that he sent, without permission, a tiny ceramic tile with miniature artworks by Robert Rauschenberg, Claes Oldenburg, Andy Warhol, and three other artists to the Moon with Apollo 12. This month, a golden urn honoring astronaut Robert Henry Lawrence Jr. will be sent into orbit.

Until recently, no one had really put together a full picture of what humans have sent off-Earth with intent of communicating something about life on this planet.

So Paul Quast, director of the Beyond the Earth Foundation, set out to catalogue every cultural artifact and intentional message humans have launched or beamed into space. Published in the International Journal of Astrobiology, his accounting is (as far as he knows) the first attempt at simply documenting what we’re sending out there—a first step toward piecing together a complete sense of what we’re signaling about our world.

“It’s reflective of how we judge ourselves and our perceived position throughout the universe,” says Quast. “It’s quite inward reflecting.” For instance, he notes that much of what we’ve sent into space is about people. But if we’re trying to tell aliens about Earth, perhaps we should try to tell them about our whole planet.

The other potential audience for the items in this collection is future humans. The items we’ve sent into space will last for generations to come. If an extraterrestrial intelligence ever does reply to one of our transmissions or intercept one of our artifacts, it could be thousands of years in the future. It would be nice if the future humans who receive the response know what we’d said to begin with. But even today, that’s not entirely clear.

“There are a lot of messages that exist as rumors,” says Quast. “I keep finding new signals, as well, which is quite unnerving to say the least.”

When we die, we leave behind information. This information can take many forms, from our genetics, replicated in future generations, to posts on the internet. We keep history trapped in photographs, videos, and stories written down into books. Sometimes, we take treasured artifacts, place them within a time capsule, and bury them underground.

Not all of this information will last, however: Elements conspire to erode our data as time passes. And that creates an urgent existential problem. There are myriad of ways that the world as we know it could come crashing down, from nuclear war to rampant climate change. But somehow, if we’re to be remembered, our information must outlast these cataclysms.

What technology will allow us to do so? How will we guarantee that, in a million years, humanity—or intelligent non-humans—will be able to access this information and understand what the 21st century was like? The possibilities run the gamut from ceramic tiles to hard drives on the Moon, each more fantastical than the next.

One privately-funded endeavor, the Memory of Mankind (MoM), is going back to basics. A small group of artists, historical archaeologists and researchers are engraving texts onto ceramic materials, which are then buried in the world’s oldest salt mine in Austria. Here, the expectation is they’ll remain intact for a million years. The idea is not too dissimilar to the cave carvings made by humans many millennia ago.

Martin Kunze, an artist and the founder of MoM, explained to Earther that these “ceramic data carriers” are resistant to extremely high temperatures, corrosive chemicals and powerful radiation. Kunze explains that it’s not meant to be a backup of all our knowledge, but a record of how we gained that knowledge. The group is particularly keen on receiving doctoral theses, which they have already started to gather.

MoM isn’t the only relatively low-tech communication tool available. Humans of the distant future might turn to trees to comprehend the past, much as we do today.

Anyone who is a fan of the animated television series Bob’s Burgers should enjoy their latest episode, which debates the merits and potential pitfalls of METI and they even mention Kardashev Type 3 civilizations!

This review does an incomplete job of describing the episode, but it has enough detail to give you an idea what was going on.

For decades, a group of researchers on a quest to find extraterrestrial life have been listening patiently to the cosmos. From their hub at the SETI Institute (a.k.a. the “Search for Extraterrestrial Intelligence”) in Mountain View, California, the researchers are searching for a signal, a radio transmission, from an extraterrestrial species.

Though there is a plausible scientific case that other life could exist out there somewhere, it could be a very long time before we detect anything. And in the meantime, there’s an important question they need to figure out: How can we recognize an alien language when we have no idea what it may sound like? How can we be sure the signal we’re receiving is a language, and not just some random noise?

These are the big questions Laurance Doyle, a research scientist at SETI, is dedicated to answering. He believes it will be possible to recognize an alien language as a language. And he bases that belief on his studies on how animals communicate with one another on Earth. Really.

According to Doyle, there are two main steps to figure out if a communication from beyond is a language. All it takes is some know-how of a branch of math called “information theory.” Recently, Doyle walked me through it.

This work is also meaningful because it directs us to look at the world around us and better understand how animals communicate with one another. It’s possible that in deeper study of communication systems on Earth, scientists will find new, interesting patterns separate from Zipf’s law.

Take the slime mold, for example. It’s a superorganism — a single body composed of thousands of individual amoeba-like creatures — that seems to communicate and have intelligence despite the fact that it doesn’t have a single neuron. How does a slime mold communicate? Scientists are still figuring it out. And in figuring it out, they could discover something new and wonderful that could help them better decipher alien communication.

I show that these signals are not astrophysical or instrumental in nature, but originate from the non-random spacings of spectral absorption lines. They can be shown to arise in their clearest form in synthetic solar spectra, as these do not suffer from noise.

“Although our result was negative, there’s still a lot we learned by creating and applying this algorithm, which could be used with other stars,” Lipman, lead author and an undergraduate at Princeton University, told Live Science. “It speaks to how much you can do with publically available data.”

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For the last twelve years, this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image: Marco Lorenzi).

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